A method and system in integrated circuit metrology for adapting a metrology system to work with diverse metrology devices. One embodiment is a method and system for generating signal adjustment data to adapt measured diffraction signals to enable use of a library of diffraction signals and structure profiles created for a different metrology device. Another embodiment is the creation and use of a data store of diffraction adjustment vectors and metrology device specifications relative to a reference device specification.
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28. A computer-readable storage medium containing stored data including:
identifying information for a primary metrology device; identifying information for one or more secondary metrology devices; identifying information for a library of diffraction signals and associated profiles; and one or more signal adjustment vectors, each signal adjustment vector determined from calculating differences between a diffraction signal generated by measuring a site on a wafer utilizing the primary metrology device and a diffraction signal generated by measuring the site on the wafer utilizing on of the one or more secondary metrology devices, wherein each signal adjustment vector is configured to adapt diffraction signals measured using the secondary metrology device to be operative with the identified library of diffraction signals and associated profiles.
1. A method in integrated circuit astrology for adapting a metrology system to work with diverse astrology devices, the method comprising:
measuring a set of sites on a wafer utilizing a first metrology device, the measurement generating a first set of diffraction signals, the first astrology device having identifying specifications; measuring the set of sites on the wafer utilizing a second metrology device, the measurement generating a second set of diffraction signals, the second metrology device having identifying specifications; calculating differences between each signal of the first set of diffraction signals and the corresponding signal of the second set of diffraction signals; and determining a signal adjustment vector from the calculated differences, the signal adjustment vector configured to enable metrology data created for the first metrology device to be used in the second astrology device.
12. A system for adapting an integrated circuit metrology system to work with a plurality of metrology devices, the method comprising:
a first metrology device configured to generate a first set of diffraction signals off a set of structures in a wafer, the first metrology device having identifying specifications; a second metrology device configured to generate a second set of diffraction signals off the set of structures in the wafer, the second metrology device having identifying specifications; and an estimator configured to calculate differences between each signal of the first set of diffraction signals and the corresponding signal of the second set of diffraction signals and configured to determine a signal adjustment vector from the calculated differences, wherein the signal adjustment vector enables metrology signal data created for use in the first metrology device to be used in the second metrology device.
26. A computer-readable storage medium containing computer executable code to adapt a metrology system to work with diverse metrology devices by instructing a computer to operate as follows:
measuring a set of sites on a wafer utilizing a first metrology device, the measurement generating a first set of diffraction signals, the first metrology device having identifying specifications; measuring the set of sites on the wafer utilizing a second metrology device, the measurement generating a second set of diffraction signals, the second metrology device having identifying specifications; calculating differences between each signal of the first set of diffraction signals and the corresponding signal of the second set diffraction signals; and determining a signal adjustment vector from the calculated differences, the signal adjustment vector configured to enable metrology data created for the first metrology device to be used in the second metrology device.
21. A system for storing integrated circuit metrology signal adjustment data and responding to request for signal adaptation, the system comprising:
a query device configured to send a query including identifying information about a metrology device and identifying information about a library of diffraction signals and associated profiles; a signal adjustment server coupled to the query device and configured to process the query and configured to format and transmit a response to the query device; and a data store couple to the signal adjustment server and configured to store signal adjustment data, identifying information about metrology devices, and identifying information about a library of diffraction signals and associated profiles, wherein the signal adjustment data includes one or more signal adjustment vectors, wherein each signal adjustment vector is determined from calculating differences between a diffraction signal generated by measuring a site on a wafer utilizing a first metrology device and a diffraction signal generated by measuring the site on the wafer utilizing a second metrology device.
10. A method in integrated circuit metrology for adapting a metrology system to work with diverse metrology devices, the method comprising:
measuring a set of sites on a wafer utilizing a first metrology device, the measurement generating a first set of diffraction signals, the first metrology device having identifying specifications; measuring the set of sites on the wafer utilizing one or more second metrology devices, each measurement generating a second set of diffraction signals, each second metrology device having identifying specifications; calculating differences between each signal of the first set of diffraction signals and the corresponding signal of the second sets of diffraction signals; determining a signal adjustment vectors from the calculated differences, each signal adjustment vector configured to enable metrology data created for the first metrology device to be used in a corresponding second metrology device; and storing data elements comprising the identifying specifications of the first metrology device, identifying specifications of the second metrology device, and the associated signal adjustment vector.
27. A computer-readable storage medium containing computer executable code to adapt a metrology system to work with diverse metrology devices by instructing a computer to operate as follows:
measuring a set of sites on a wafer utilizing a first metrology device, the measurement generating a first set of diffraction signals, the first metrology device having identifying specifications; measuring the set of sites on the wafer utilizing one or we second metrology devices, each measurement generating a second set of diffraction signals, each second metrology device having identifying specifications; calculating differences between each signal of the first set of diffraction signals and the corresponding signal of the second sets of diffraction signals; determining a signal adjustment vectors from the calculated differences, each signal adjustment vector configured to enable metrology data created for the first metrology device to be used in a corresponding second metrology device; and storing date elements comprising the identifying specifications of the first metrology device, identifying specifications of the second metrology device, and the associated signal adjustment vector.
2. The method of
3. The method of
4. The method of
measuring a diffraction signal off an integrated circuit structure using the second metrology device, the measurement generating a measured structure diffraction signal; calculating an adjusted diffraction signal utilizing the measured structure diffraction signal and the signal adjustment vector; selecting a best match of the adjusted diffraction signal compared to diffraction signals in the library of diffraction signals and corresponding profile dara, the library created for the first metrology device; and accessing the profile data corresponding to the selected best match library diffraction signal.
5. The method of
6. The method of
7. The method of
8. The method of
9. The method of
storing the signal adjustment vector and identifying specifications of the first and second metrology device.
11. The method of
13. The system of
14. The system of
15. The system of
a profile library configured to contain diffraction signals and associated profile data; and a profile application server configured to process measured diffraction signals and select a best match of to measured diffraction signal compared to the diffraction signal of the profile library.
16. The system of
a data store coupled to the profile application server, the data store configured to store one or more signal adjustment vectors and metrology tool identifying specifications.
18. The system of
19. The system of
20. The system of
22. The system of
23. The system of
24. The system of
25. The system of
a fabrication system coupled to the query device, the fabrication system including a lithography unit and/or an etch unit.
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This application relates to co-pending U.S. patent application Ser. No. 09/727,530, entitled "System and Method for Real-Time Library Generation of Grating Profiles" by Jakatdar, et al., filed on Nov. 28, 2000, to co-pending U.S. patent application Ser. No.(To be assigned) entitled "Metrology Hardware Specification Using a Hardware Simulator" by Bao, et al., filed on Mar. 26, 2002, and to co-pending U.S. patent application Ser. No. 09/737,705 entitled "System and Method for Grating Profile Classification" by Doddi, et al., filed on Dec. 14, 2000, all owned by the assignee of this application and incorporated herein by reference.
1. Field of the Invention
The present invention relates to metrology for semiconductor manufacturing applications, and in particular to a method and system for adapting metrology systems to work with different metrology devices.
2. Related Art
As integrated circuits (IC's) evolve towards smaller critical dimensions (CD's) and faster response time, new challenges are encountered in the manufacturing processes. Accurate metrology for measurement of features with sizes on the order of 100 nm or smaller is desirable.
Optical metrology has emerged as an effective tool, with several advantages over other metrology methods such as Scanning Electron Microscopy (SEM). Optical probes are non-destructive, can be employed in production monitoring and control, and can be used for determination of thickness and topographic information as well as for CD measurement.
Known methods in scatterometry are used to reconstruct a diffraction grating profile from its optical diffraction responses, at a fixed incident angle and multiple wavelengths. A library-based methodology for profile extraction utilizes libraries of diffraction signals and simulated grating profiles which include such detailed profile characteristics as: rounding, footing, T-topping, material thickness variation, sidewall angles, and CD variation. Mask information, thin-film information such as parameters describing optical properties n & k, and thickness values, are inputs which are used to compute the diffraction signal of a collection of simulated profiles. To determine the profile of an integrated circuit structure, the diffraction signal is measured for that structure and compared with the library of simulated diffraction signals, and a best match is found, i.e., a profile whose simulated diffraction signal best matches the actual measured diffraction signal.
The diffraction signals are typically calculated by a grating response simulator which utilizes Rigorous Coupled-Wave Analysis (RCWA) analytical techniques, as described in the article "Specular Spectroscopic Scatterometry", IEEE Transactions on Semiconductor Manufacturing, Vol. 14, No. 2, May 2001, pp 97-111, by Niu et al. Other simulation algorithms may also be used to calculate the spectral scattering responses or diffraction signals. An integral method is described in "Numerical Methods for the Analysis of Scattering from Nonplanar Periodic Structures", A. R. Neureuther and K. Zaki, Int'l URSI Symposium on Electromagnetic Waves, Stresa, Italy, pp 282-285, 1969. A differential method is described in "Systematic Study of Resonances Holographic Thin Film Coulers", M Neviere et al, Optics Communications, Vol. 9, No. 1, pp 48-53, September 1973.
The hardware used in conjunction with metrology, which may include a metrology beam source, ellipsometer, reflectometer, and the like, is subject to parameters, which are not exactly reproducible. Examples of hardware-related variable parameters include: angle of metrology beam incidence, numerical aperture, wavelength range, polarization, and noise. The variation in hardware causes problems relating to metrology. The library diffraction signals are calculated according to inputs based on a particular set of hardware specifications, and according to ideal material characteristics. If the actual pieces of hardware and batch of material used in the measurement of a sample's diffraction signal have slightly different specifications or characteristics than those used in the library calculations, inaccuracies may be incurred when matching the measured diffraction signal to the calculated library diffraction signals. Typically, a library of diffraction signals and associated profile data is created for a specific metrology hardware model and other parameters. This library may not provide accurate results when used for another metrology tool even for a similar hardware device from the same manufacturer and the same model.
The present invention includes a method and system in integrated circuit metrology for adapting a metrology system to work with diverse metrology devices. The method comprises measuring a set of sites on a wafer with a first metrology device and a second metrology device, calculating differences between signals of the first set of diffraction signals and the corresponding signals of the second sets of diffraction signals and determining signal adjustment vectors. The signal adjustment vector is configured to enable metrology data created for the first metrology device to be used in a corresponding second metrology device, the metrology data may be a library of simulated diffraction signals and associated profiles. In one embodiment, identifying information about the first and the second metrology devices plus the associated signal adjustment vectors may be stored in a data store.
Another embodiment is a system for storing integrated circuit metrology signal adjustment data and responding to request for signal adaptation, the system comprising a query device configured to send a query including identifying information about a metrology device and identifying information about a library of diffraction signals and associated profiles, a signal adjustment server coupled to the query device and configured to process the query and further configured to format and transmit a response to the query device; and a data store coupled to the signal adjustment server and configured to store a signal adjustment data, identifying information about a metrology device, and identifying information about a library of diffraction signals and associated profiles.
One embodiment of the present invention includes a method and system for adapting metrology data created to work with one metrology setup to become operative in another metrology setup. In order to facilitate description of the concepts and principles of the current invention, an exemplary ellipsometric optical metrology system will be discussed. However, the same concepts and principles equally apply to other optical metrology system such as reflectometric systems and the like, as well as other metrology systems wherein a library or database of diffraction signals and structure profiles are used.
Referring to
As an illustrative example,
In one embodiment, the differences at each wavelength measurement point are averaged out for all the selected sites on the wafer, the differences calculated from measurements of the primary and secondary metrology tools.
One embodiment includes a method of using correction graphs to adapt measurements performed with one metrology tool to use a library generated for use with another metrology tool. The difference between measurements of two tools for the same sites may also be expressed as a signal adjustment vector where the elements of the vector are the averaged measurement differences at the measurement points for the metrology tools used. For example, if a metrology tool takes diffraction signal measurement at 50 points in the wavelength range used for the tool, the signal adjustment vector would have 50 elements. Each element of the signal adjustment vector is a calculated average of the signal differences at the measurement point. As mentioned above, the vector elements may be calculated by simple averaging, by statistical averaging techniques, or by clustering of the measurement differences and determining a center for the cluster. For a description of a clustering algorithm using a heuristic to provide a near optimal solution, refer to co-pending U.S. patent application Ser. No. 09/737,705 entitled "System and Method for Grating Profile Classification" by Doddi, et al., filed on Dec. 14, 2000 which is incorporated in its entirety herein by reference.
In this example, to confirm the results of the method, a specific site measured by both Tool 1 and Tool 2 was selected, Site 4.
Still referring to
There are several applications of the concepts and principles of the present invention. For example, a standard or "ideal" library of diffraction signals and associated profiles may be created for a standard or "ideal" metrology tool. Using a standard wafer with a specified number of sites, the sites are measured using one or more metrology tools similar to the standard metrology tool. Following the process steps discussed above, a signal adjustment vector is calculated for the one or more metrology tools. The signal adjustment vector may be saved in a data store together with identifying information for the library and the specific metrology tool. By associating a signal adjustment vector with identifying library and tool information, a metrology tool may be used with different libraries for as long as a signal adjustment vector had previously been calculated. The data store containing the signal adjustment vectors may be stored in a centralized data store and accessed as needed through a networked connection.
It is not intended that the invention be restricted to the exact embodiments described herein. It is clear to one skilled in the art that modifications to the exact method can be made without departing from the inventive concept. The method may be used not only to calibrate the library diffraction signal between different pieces of hardware, but also to calibrate the library diffraction signal over time for a single piece of hardware, to compensate for wear-induced drifting of hardware parameters. In addition to spectroscopic ellipsometers and reflectometers, the method of the present invention of utilizing an adjustment vector may also be applied to other optical metrology tools utilizing specialized beams such as lasers and to other kinds of metrology tools such as electron, or mechanical metrology devices. Examples of electron metrology devices include CD-scanning electron microscope (CD-SEM), transmission electron microscope (TEM), and focused ion beam (FIB) devices. An example of a mechanical metrology device is an atomic force microscope (AFM). The scope of the present invention should be construed in view of the claims that follow.
Jakatdar, Nickhil, Laughery, Michael, Wasinger, David
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